Electric motor with retainer disc and method for assembling same

ABSTRACT

The invention relates to an electric motor and a method for assembling the motor. Especially preferred is that the electric motor is for driving an antiroll stabilizer. The electric motor includes firstly a stator having at least one electromagnet and a rotor which can rotate about an axis relative to the stator. The electric motor also includes at least one bearing plate for receiving a bearing for rotatable mounting of the rotor. Disposed on the bearing plate is a retainer disc for retaining contacts. The contacts are for electrical connection of the at least one electromagnet of the stator and pass through the retainer disc. Fastening elements are used to fasten the retainer disc to the bearing plate. There is also a positioning arrangement for radial positioning of the retainer disc with respect to the bearing plate. According to the invention the positioning arrangement is designed for adjustable radial positioning of the retainer disc with respect to the bearing plate.

BACKGROUND

The present invention relates to an electric motor that has a retainerdisc mounted on a bearing plate for holding contacts. The electric motoris provided, in particular, for applications in motor vehicles, forexample, for driving an electromechanical roll stabilizer, for driving asteering system, or for driving a ride-height control system. Inaddition, the invention relates to a method for assembling the motoraccording to the invention.

DE 10 2012 205 754 A1 shows a housing for a rotating electrical machinewith a bearing plate between a housing outer part and a housing innerpart. A rotor position sensor is mounted on a sensor holder.

DE 10 2010 000 710 A1 shows a bearing plate for an electric motor thathas a current guide that is designed to connect at least one winding ofthe stator to a current connection.

From DE 299 01 976 U1, an electric motor is known with an arrangementfor monitoring the rotational speed in which a sensor element isarranged so that it can be connected to an inner wall of a bearingplate.

FIG. 3 shows a cross section of a detail of an electric motor accordingto the prior art. The electric motor comprises a stator 01 and a rotor02. The rotor 02 can be rotated relative to the stator 01 about an axis03. The rotor 02 comprises a rotor shaft 04 that is supported so that itcan rotate in a bearing 06. The bearing 06 sits in a bearing plate 07that is mounted on a motor housing 08. The motor housing 08 with thestator 01 located therein and bearing plate 07 are mounted within asystem housing 09.

The stator 01 comprises an electromagnet (hidden in the illustration)out of which multiple conductors 11 project for the electricalconnection of the electromagnet. The electromagnet of the stator 01comprises a laminated core with windings (not shown) located on thiscore. The conductors 11 are guided through the bearing plate 07. On thebearing plate 07 there is a retainer disc 12 made from a plastic forholding contacts 13. The retainer disc 12 is arranged coaxial to theaxis 03 and axially next to the bearing plate 07. The retainer disc 12is mounted on one side with screws 14 on the bearing plate 07. On theother side, the retainer disc 12 has guide pins 16 that determine theradial position of the retainer disc 12. In addition, the contacts 13are mounted on the conductors 11 of the electromagnet of the stator 01so that the position of the retainer disc 12 is overdetermined relativeto the bearing plate 07. This can lead to mechanical voltages on thecontacts 13 that can have effects on a power electronics module 17 thatis connected rigidly to the contacts 13 with the help of contact screws18. In particular, this can lead to deformation of a printed circuitboard 19 of the power electronics module 17. The deformation is shown bya dimension s.

The retainer disc 12 further has sensor guide pins 21 for determiningthe radial position of a sensor electronics module 22. The sensorelectronics module 22 is opposite an angular position and rotationalspeed encoder 23 that is made from a permanently magnetic material andis mounted on the rotor shaft 04. The sensor electronics module 22 andthe angular position and rotational speed encoder 23 form a rotationalspeed sensor for measuring the rotational speed of the electric motor.The over-fixing of the position of the retainer disc 12 described abovecan lead to displacements of the retainer disc 12 which lead, in turn,to displacements of the sensor electronics module 22 in the form of aneccentricity e and therefore can negatively affect the accuracy of therotational speed sensor.

FIG. 4 shows the retainer disc 12 shown in FIG. 3 in a plan view. Thescrews 14 (shown in FIG. 1) are guided by circular round fasteneropenings 24 in the retainer disc 12. The fastener openings 24 are eachformed within a metallic insert bushing that is inserted into theretainer disc 12.

SUMMARY

The objective of the present invention is to increase the accuracy ofthe positioning of retainer discs relative to a bearing plate in anelectric motor starting from the known prior art.

The specified object is achieved by an electric motor according to oneor more features of the invention and by a method.

The electric motor according to the invention is used for the rotationaldrive of a machine element, preferably for the rotational drive of amachine element of a vehicle. In an especially preferred way, theelectric motor is formed for driving an electromechanical rollstabilizer, for driving a steering system, or for driving a ride-heightcontrol system of a motor vehicle. The electric motor according to theinvention first comprises a stator with at least one electromagnet thatpreferably has a laminated core with windings located on this core. Thestator preferably comprises multiple electromagnets for a multi-phaseoperation of the electric motor. The electric motor further comprises arotor that can rotate relative to the stator about an axis. The rotorpreferably has a permanent magnet. The electric motor comprises at leastone bearing plate for holding a bearing for the rotational support ofthe rotor. The bearing plate is arranged at an axial end of the stator.If two of the bearing plates are present, each of the bearing platesforms an axial termination of the stator. The bearing is preferably aroller bearing. The bearing sits fixed in the bearing plate and is heldby this plate relative to the stator.

On the bearing plate there is a retainer disc for holding contacts. Thecontacts are used for the electrical connection of the at least oneelectromagnet of the stator and are guided through the retainer disc.The contacts sit fixed in the retainer disc.

The electric motor further comprises individual fasteners for fasteningthe retainer disc on the bearing plate. The retainer disc is mounted onthe bearing plate with the help of fasteners.

The electric motor further comprises a positioning arrangement for theradial positioning of the retainer disc relative to the bearing plate.

According to the invention, the positioning arrangement is formed forthe variable radial positioning of the retainer disc relative to thebearing plate. The positioning arrangement thus allow the radialposition of the retainer disc to change relative to the bearing platebefore the retainer disc is mounted on the bearing plate with the helpof the fasteners.

The retainer disc preferably has a shape that permits radial movement ofthe retainer disc relative to the bearing plate before the retainer discis fastened. After the retainer disc is fastened, the radial movement ofthe retainer disc relative to the bearing plate is prevented directlyjust by the fasteners. Thus, the shape of the retainer disc and theshape of the bearing plate do not determine the position of the retainerdisc relative to the bearing plate, but instead ultimately thefasteners. While the shape of the retainer disc and the shape of thebearing plate enable the degree of freedom of the retainer disc in theradial direction at least for a movement in the scope of play, thefasteners permit no degree of freedom of the retainer disc. Inparticular, the retainer disc has no positive-fit guidance, inparticular, no guide elements, which determine the radial position ofthe retainer disc relative to the bearing plate completely and withoutplay due to their shape. The retainer disc is preferably connected tothe bearing plate not with a positive fit connection in the radialdirection. The specified radial direction is with respect to the axis ofthe electric motor.

A special advantage of the electric motor according to the invention isprovided in that, due to the variable adjustability of the positioningarrangement and due to an elimination of a positive-fit guide, multipleproblems of the solutions according to the prior art are avoided.

The fasteners are preferably formed for non-positive-fit oradhesive-bond fastening of the retainer disc on the bearing plate. Thesefasteners enable an adjustment of the radial position of the retainerdisc relative to the bearing plate during assembly. This adjustment isnot prevented by the shape of the retainer disc. In particular, no guideelements of the retainer disc prevent such adjustment. In each case, theshape of the retainer disc and the shape of the bearing plate determinethe radial position of the retainer disc relative to the bearing plateat least not completely, but instead allow at least radial play beforethe retainer disc is mounted on the bearing plate with the help of thefasteners.

The fasteners and the retainer disc are formed preferably by individualcomponents. The fasteners and the retainer disc are not constructedintegrally as one unit.

The electric motor preferably has a cylindrical lateral surface-shapedhousing that surrounds at least the stator and the bearing platecircumferentially. The electric motor can also have another housing, forexample, a system housing that surrounds additional components of theelectric motor.

The retainer disc is preferably arranged in the axis of the electricmotor so that the retainer disc is arranged coaxial to the rotor andstator. The bearing plate is also preferably arranged in the axis of theelectric motor so that the retainer disc and the bearing plate are alsoarranged coaxial to each other.

The retainer disc is preferably arranged axially adjacent to the bearingplate. In an especially preferred way, the retainer disc is arrangedaxially directly adjacent to the bearing plate. The bearing plate ispreferably arranged axially between the stator and the retainer disc.Consequently, the retainer disc is arranged farther outside than thebearing plate.

The retainer disc preferably has the outer shape of a flat cylinder, inparticular, a flat hollow cylinder. The retainer disc is made preferablyfrom a plastic.

The fasteners are preferably arranged at a distance to the axis. Thefasteners extend preferably parallel to the axis.

The fasteners are preferably guided through fastener openings in theretainer disc. Thus, the fasteners cause a non-positive-fit connectionbetween the retainer disc and the bearing plate.

The fasteners preferably have a cylindrical base shape. The fastenersare preferably formed by screws or rivets. The electric motor preferablycomprises between two and five of the fasteners, in an especiallypreferred way, exactly three of the fasteners.

The positioning arrangement is preferably formed in or on the retainerdisc.

The positioning arrangement is preferably formed by the fasteneropenings in the retainer disc. Here, the fastener openings have a largercross section than the fasteners so that the fasteners allow a radialplay of the retainer disc relative to the bearing plate with respect tothe axis of the electric motor as long as the fastening process with thefasteners is not yet completed. In each case, due to the larger crosssection of the fastener openings, the exact radial position of theretainer disc relative to the bearing plate is not yet predefined.

The fastener openings with the larger cross section preferably have anelliptical or an oval cross section, wherein a longer axis of theelliptical or oval cross section is arranged parallel to a radius thatextends on the retainer disc from the axis to the contacts. This shapeof the fasteners allows an alignment of the retainer disc duringassembly through a radial displacement of the contacts, so that thecontacts can be oriented relative to the elements to be connected to thecontacts and later over-fixing after completion of the assembly isprevented.

The fastener openings are preferably each formed within a metallicinsert bushing that is sunk into the retainer disc and forms an integralcomponent of the retainer disc.

The metallic contacts are preferably mounted by injection molding in theretainer disc made from plastic. This type of fastener can indeed leadto an inexact position of the contacts in the retainer disc, but thisinexactness due to the lack of a positive-fit connection in the radialdirection between the retainer disc and the bearing plate does notresult in over-fixing of the position of the retainer disc.

The contacts are preferably arranged spaced-apart to the axis. Thecontacts extend preferably parallel to the axis. The contacts arepreferably formed by metallic conductor elements.

The contacts are preferably mounted on conductors extending out from theelectromagnet, in order to create an electrical connection between thecontacts and the electromagnet so that current can flow to theelectromagnet of the stator via the contacts. The contacts arepreferably welded onto the conductors projecting out from theelectromagnet.

In preferred embodiments of the electric motor according to theinvention, this further comprises a power electronics module that isconnected rigidly to the contacts guided through the retainer disc.Here, the retainer disc is arranged axially between the stator and thepower electronics module so that the contacts form an electricalconnection running through the retainer disc between the powerelectronics module and the electromagnet of the stator. The powerelectronics module is preferably mounted with contact fasteners to thecontacts of the retainer disc. The contact fasteners are preferablyformed by contact screws. The power electronics module is used for theelectrical control of the electric motor.

The power electronics module is preferably arranged axially directlyadjacent to the retainer disc. The power electronics module is arrangedpreferably spaced-apart to the axis. Preferably, the power electronicsmodule is located on the circumference of the electric motor, forexample, directly under a cylindrical lateral surface-shaped housing ofthe electric motor.

The power electronics module preferably comprises a printed circuitboard that extends parallel to the axis of the electric motor. Theprinted circuit board is preferably connected rigidly to the contacts ofthe retainer disc. The printed circuit board and the contacts arepreferably arranged at an equal distance to the axis.

In preferred embodiments of the electric motor according to theinvention, this further comprises a rotational speed sensor. Therotational speed sensor preferably comprises an angular position and/orrotational speed encoder connected rigidly to the rotor and a sensorelectronics module whose radial position is defined directly by thebearing plate. In contrast to the prior art, the radial position of thesensor electronics module is not defined by the retainer disc so thatover-fixing of the retainer disc is prevented. Radial displacement ofthe retainer disc can also not have the result that the accuracy of therotational speed sensor is negatively affected.

The sensor electronics module is preferably arranged in the axis of theelectric motor. The retainer disc is preferably arranged between thebearing plate and the sensor electronics module. The power electronicsmodule and the sensor electronics module are preferably located at thesame axial position.

The sensor electronics module preferably has guide pins by which it isguided in the bearing plate, whereby the radial position of the sensorelectronics module is defined. For this purpose, the bearing platepreferably has guide openings that hold the guide pins without play. Theguide pins are guided through guide pin openings in the retainer disc,which hold the guide pins with play. The guide pins are preferablyspaced apart and oriented parallel to the axis of the electric motor.

The guide pin openings in the retainer disc have a larger cross sectionthan the guide pins. Thus, the sensor electronics module and theretainer disc can be slightly displaced in the radial direction duringassembly without the guide pins of the sensor electronics module and theretainer disc contacting against each other and this resulting in anover-fixing of the position of the retainer disc.

The guide pin openings preferably have an ellipse-like or oval crosssection, wherein a longer axis of the ellipse-like or oval cross sectionis arranged parallel to a radius that extends on the retainer disc fromthe axis to the contacts. This shape of the guide pin openings allows analignment of the retainer disc during assembly by a radial displacementof the contacts, so that the contacts can be oriented relative to theelements to be connected to the contacts and later over-fixing aftercompletion of the assembly is prevented.

The electric motor according to the invention can comprise additionalelectronics modules, in particular, additional sensor electronicsmodules, e.g., a temperature sensor electronics module, which are guidedin the same way as the sensor electronics module of the rotational speedsensor with the help of guide pins in the bearing plate.

The method according to the invention is used for assembling theelectric motor according to the invention. In one step of this method,an axial positioning of the retainer disc next to the bearing plate isrealized. An alignment of the retainer disc relative to the bearingplate in the radial direction is also realized, in order to set, inparticular, the exact position of the contacts. This alignment ispossible, because the positioning arrangement is formed according to theinvention for the variable radial positioning of the retainer discrelative to the bearing plate. After the radial alignment, the retainerdisc is mounted on the bearing plate by attaching the fasteners.Furthermore, the contacts are mounted on the electromagnet of thestator, which is also realized after the radial alignment of theretainer disc.

One special advantage of the method according to the invention is thatthe assembly does not lead to over-fixing of the position of theretainer disc. Thus, deviations of the position of the contacts in theretainer disc cannot have the result that the retainer disc becomeswarped. Such deviations could be produced if the retainer disc is madefrom plastic when the metallic contacts are injection molded.

The electric motor to be produced according to the method according tothe invention preferably also has such features that are specified aspreferred for the electric motor according to the invention.

For the radial orientation of the retainer disc, preferably a gauge isused that represents a minimum permissible distance between the contactsand an inside of a housing of the electric motor. This distancecorresponds to a height of the power electronics module that can bedetermined, in particular, by a cooling body of the power electronicsmodule. The use of the gauge guarantees that a sufficiently large spaceis maintained in the interior of the electric motor for the powerelectronics module to be installed and the assembly does not lead tomechanical stresses that can act, in particular, on the retainer disc.The gauge is preferably formed by a prism.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages, details, and refinements of the invention are givenfrom the following description of a preferred embodiment of the electricmotor according to the invention with reference to the drawing. Shownare:

FIG. 1: a cross section of a detail of a preferred embodiment of anelectric motor according to the invention,

FIG. 2: a retainer disc shown in FIG. 1 in a plan view,

FIG. 3: a cross section of a detail of an electric motor according tothe prior art, and

FIG. 4: a retainer disc shown in FIG. 3 in a plan view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross section of a detail of a preferred embodiment of anelectric motor according to the invention. The electric motor comprisesa stator 31 and a rotor 32. The rotor 32 can be rotated relative to thestator 31 about an axis 33. The rotor 32 comprises a rotor shaft 34 thatis supported so that it can rotate in a roller bearing 36. The rollerbearing 36 sits in a bearing plate 37 that is mounted on a motor housing38. The motor housing 38 with the stator 31 and bearing plate 37 locatedin this housing are mounted within a system housing 39.

The stator 31 comprises an electromagnet (hidden in the illustration)from which multiple conductors 41 project for the electrical connectionof the electromagnet. The electromagnet of the stator 31 comprises alaminated core with windings (not shown) located on this core. Theconductors 41 are guided through the bearing plate 37. A retainer disc42 made from a plastic for holding contacts 43 sits on the bearing plate37. The retainer disc 42 is arranged coaxial to the axis 33 and axiallynext to the bearing plate 37.

The retainer disc 32 is mounted only with screws 44 on the bearing plate37. The retainer disc 32 has no direct positive-fit connection to thebearing plate 37 that determines the radial position of the retainerdisc 12 relative to the bearing plate 37.

The contacts 43 are mounted on the conductors 41 of the electromagnet ofthe stator 31, which, however, does not lead to an over-fixing of theposition of the retainer disc 42 in the electric motor according to theinvention, because the welding of the contacts 43 is realized with theconductors 41 only after a radial orientation of the retainer disc 42relative to the bearing plate 37.

The electric motor further comprises a power electronics module 47 witha printed circuit board 49 that is connected rigidly to the contacts 43with the help of contact screws 48. In the electric motor according tothe invention, however, no mechanical stress acts on the powerelectronics module 47 and especially on the printed circuit board 49,because the retainer disc 42 is oriented in the radial direction withthe help of a gauge (not shown) so that a distance h (shown in FIG. 3)is guaranteed between the contacts 43 and the system housing 39.

The electric motor further comprises a rotational speed sensor formeasuring the rotational speed of the electric motor. The rotationalspeed sensor is formed by a sensor electronics module 52 and by anangular position and rotational speed encoder 53 which are opposite eachother. The angular position and rotational speed encoder 53 consists ofa permanently magnetic material and is mounted on the rotor shaft 34.

The sensor electronics module 52 has guide pins 54 with which it isguided in guide openings 56 in the bearing plate 37, whereby a radialposition of the sensor electronics module 52 is defined. The guideopenings 56 hold the guide pins 54 in an accurately fitting way so thatthe radial position of the sensor electronics module 52 is defined by apositive fit connection with the bearing plate 37. The guide pins 54project with a clear play through guide pin openings 57 into theretainer disc 42 so that the guide pin openings 57 do not define theradial position of the guide pins 54.

FIG. 2 shows the retainer disc 42 shown in FIG. 1 in a plan view. Thescrews 44 (shown in FIG. 1) are guided through oval fastener openings 58in the retainer disc 42. The oval cross section of the fastener openings58 is oriented such that the longer axis of the oval is orientedparallel to a radius of the circular shape of the retainer disc 42 thatextends from the axis 33 to the contact 43. The oval fastener openings58 are each formed within a metallic insert bushing that is sunk intothe retainer disc 42. Due to their oval cross section, the oval fasteneropenings 58 permit a variable radial positioning of the retainer disc 42relative to the bearing plate 37 before the retainer disc 42 was mountedon the bearing plate 37 with the help of the screws 44.

The guide pin openings 57 also have an oval cross section whose longeraxis is oriented parallel to the specified radius of the circular shapeof the retainer disc 42 that extends from the axis 33 to the contact 43.

The oval cross sections of the fastener openings 58 for the screws 44and the guide pin openings 57 allow the retainer disc 42 to be displacedduring the assembly of the electric motor radially in the direction ofthe contacts 43, in order to prevent an over-fixing by the fastening ofthe contacts 43 and the screws 44.

LIST OF REFERENCE NUMBERS

-   01 Stator-   02 Rotor-   03 Axis-   04 Rotor shaft-   06 Bearing-   07 Bearing plate-   08 Motor housing-   09 System housing-   11 Conductor-   12 Retainer disc-   13 Contact-   14 Screw-   16 Guide pin-   17 Power electronics module-   18 Contact screw-   19 Printed circuit board-   21 Sensor guide pin-   22 Sensor electronics module-   23 Angular position and rotational speed encoder-   24 Fastener opening-   31 Stator-   32 Rotor-   33 Axis-   34 Rotor shaft-   36 Roller bearing-   37 Bearing plate-   38 Motor housing-   39 System housing-   41 Conductor-   42 Retainer disc-   43 Contact-   44 Screw-   47 Power electronics module-   48 Contact screw-   49 Printed circuit board-   52 Sensor electronics module-   53 Angular position and rotational speed encoder-   54 Guide pin-   56 Guide opening-   57 Guide pin opening-   58 Fastener opening

The invention claimed is:
 1. An electric motor comprising: a stator withat least one electromagnet; a rotor that is rotatable relative to thestator about an axis; a bearing plate that holds a bearing forsupporting the rotor, a retainer disc arranged on the bearing plate andthrough which contacts are guided for electrical connection of theelectromagnet of the stator and are held by the retainer disc, fastenersthat fasten the retainer disc on the bearing plate, and a positioningarrangement that radially positions the retainer disc relative to thebearing plate, the positioning arrangement is configured for a variableradial positioning of the retainer disc relative to the bearing plate.2. The electric motor according to claim 1, wherein the positioningarrangement is constructed in the retainer disc.
 3. The electric motoraccording to claim 2, wherein the positioning arrangement is formed byfastener openings in the retainer disc, the fasteners are guided throughthe fastener openings in the retainer disc and the fastener openingshave a greater cross section than the fasteners.
 4. The electric motoraccording to claim 3, wherein the fastener openings have anellipse-shaped cross section or an oval cross section, and a longer axisof the ellipse-shaped cross section or the oval cross section isarranged parallel to a radius that extends on the retainer disc from theaxis to the contacts.
 5. The electric motor according to claim 1,wherein further comprising a power electronics module connected rigidlyto the contacts guided through the retainer disc.
 6. The electric motoraccording to claim 1, further comprising a rotational speed sensor thatcomprises at least one of an angular position or rotational speedencoder and a sensor electronics module connected rigidly to the rotorwhose radial position is defined relative to the bearing plate.
 7. Theelectric motor according to claim 6, wherein the sensor electronicsmodule has guide pins by which said sensor electronics module is guidedon the bearing plate, the guide pins are guided through guide pinopenings in the retainer disc that have a larger cross section than theguide pins.
 8. The electric motor according to claim 7, wherein theguide pin openings have an ellipse-shaped cross section or an oval crosssection, and a longer axis of the ellipse-shaped cross section or theoval cross section is arranged parallel to a radius that extends on theretainer disc from the axis to the contacts.
 9. A method for mounting anelectric motor according to claim 1, comprising the following steps:axially positioning the retainer disc next to the bearing plate,radially aligning the retainer disc opposite the bearing plate,fastening the retainer disc on the bearing plate by attachment of thefasteners, and fastening the contacts on the electromagnet of thestator.
 10. The method according to claim 9, wherein the radiallyaligning of the retainer disc opposite the bearing plate is carried outwith a gauge that represents a minimum permissible distance between thecontacts and an inside of a housing of the electromagnet.